Influenza B virus hemagglutinin, Victoria lineage (HA)

Influenza B virus hemagglutinin (HA), Victoria lineage, is a major surface glycoprotein found on influenza B viruses, specifically those within the Victoria lineage[2][7]. It is a class I viral fusion protein that mediates viral entry by binding to sialylated glycan receptors on human respiratory epithelial cells and triggering fusion of viral and host membranes following endocytosis and exposure to acidic pH[3][7]. HA is translated as a precursor (HA0) and cleaved into two subunits: HA1 (responsible for receptor binding and antigenicity) and HA2 (drives fusion)[3][1]. Sequence variation and antigenic drift in the Victoria lineage hemagglutinin play a critical role in epidemic spread, immune escape, and vaccine updates[2][4]. The protein is a primary target for neutralizing antibodies, vaccine design, and the development of broadly protective influenza therapeutics[6]. Monitoring of HA mutations and antigenic clusters is essential for epidemiology and the annual selection of influenza B vaccine strains[4][7].

Other names

Hemagglutinin (HA)Influenza B hemagglutininB/Victoria/2/1987 HAVictoria lineage HASometimes informally referred as "flu B HA (Victoria)"

Antiviral antibodies: Bind HA, block receptor attachment, prevent fusion, or induce immune clearance; Fusion inhibitors: Prevent low-pH HA conformational rearrangement needed for fusion; Vaccine-induced protection: Elicits neutralizing antibodies against HA antigenic sites to prevent infection